SOUTH BEND, Ind. — Blood banks are declaring fewer critical shortages these days and in some cases cutting staff in response to dwindling demand for blood — the result of fewer elective surgeries being performed and medical advances that curb bleeding in the operating room.

The nation’s blood-collection system has undergone a dramatic change from just a decade ago, when agencies that oversee the blood supply worried whether they could keep up with the needs of an aging population.

Now blood banks are making fewer but more targeted appeals for donations and reducing the size of their operations.

Blood centers shifted “from a collect-as-much-as-you-can mentality to a collect-to-need mentality,” said Dr. Darrell Triulzi, medical director for the Institute for Transfusion Medicine in Pittsburgh and a former president of AABB, formerly known as the American Association of Blood Banks. “They started collecting only what they needed. That’s new to the industry. We’re still learning how to do that well.”

Job cuts have been a part of the process.

The Indiana Blood Center announced in June that it would eliminate 45 positions in a restructuring that also involved reducing its mobile operations, closing a donor center and cutting other costs because demand from hospitals had fallen 24 percent from the previous year.

The Community Blood Center of the Ozarks in Springfield, Mo., announced in March that it was cutting staff by nearly 18 percent. Blood centers in Florida, West Virginia and Connecticut have taken similar steps.

The blood-collection system began changing dramatically with the Great Recession, when Americans who had lost their jobs and health insurance put off non-critical procedures.

The need for blood is still falling even as the economy recovers. Demand dropped by 8.2 percent from 2008 to 2011 and continues to drop, according to a report by the AABB.

Contributing to the decline are blood-management programs, which include collecting blood lost during an operation and returning it to the patient, maximizing hemoglobin levels to prevent anemia and using medications to reduce bleeding during surgery.

Blood-management programs have been around for more than a decade, but have only started catching on in larger numbers in the past several years, Triulzi said. The AABB surveyed hospitals and blood centers about blood-management programs in 2011 and found nearly a third of hospitals surveyed had started such programs.

Advances in surgical methods, including laparoscopic techniques that use small “keyhole” incisions, have also curbed the need for blood.

Experts say that doesn’t mean there’s a blood glut, but there are fewer times when blood banks declare shortages and issue urgent pleas for donations, which were once commonplace.

Instead, blood centers have altered their approach, holding fewer drives and often targeting people with specific blood types. Some are even offering gas cards, T-shirts or the chance to win tickets to NFL football games as incentives.

Type O Negative blood, for example, is the most sought-after because it can be transfused into any patient. It is frequently used in emergency situations before caregivers are able to determine the blood type of the recipient. Only about 7 percent of the population has O Negative blood, yet it makes up 13 percent of blood used by the Indiana Blood Center.

“So we have to over-collect that blood group,” said Dr. Dan Waxman, the center’s executive vice president and chief medical officer.

The South Bend Medical Foundation in Mishawaka in August flashed a message to passing motorists offering those with Type O blood a $10 gas card if they donated.

Experts say there’s also strong demand for platelets, Type AB plasma, which is used in trauma and burn victims and cancer patients, and red blood cells, which are given to accident and gunshot victims and used in elective surgeries.

“I hope that people don’t read that news and say, ‘Oh, there’s not a need for me.’ Because people need blood every single day,” said Barb Kain, spokeswoman for Blood Systems in Scottsdale, Ariz., which provides blood to hospitals in 18 states.

The Indiana Blood Center recently declared a critical shortage, which Waxman said arose because summer is usually a slower time for donations. The center receives about 30 percent of its blood from high school and college students who are less likely to give during the summer.

Donors at a recent blood-collection drive in Indianapolis say they don’t plan to change their habits.

Chris Page, a 53-year-old military liaison for a job-placement company, said he used to contribute regularly but had not done so in a while. He decided to donate again after learning of a blood drive in his office building.

Jim Valmore, a 70-year-old retired electrical engineer from Indianapolis, started donating blood platelets 28 years ago when a secretary where he worked was diagnosed with a brain tumor. He donates every two weeks and has been honored by the Indiana Blood Center for giving 47 gallons of blood.

“I do it just because I can. It doesn’t cost me anything. It takes a little bit of my time,” he said. “It’s like donating to any other cause. To me, it feels good to share what I can share.”

Keeping donors like Page and Valmore in the pipeline is essential even with lower demand. Blood usually has a shelf life of 42 days, and some donated blood typically has to be discarded because of screening issues or other problems.

Kain said the decrease in demand has strengthened the supply line.

“The blood supply across the country is stronger than it has been in a long time,” she said.